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The goal of this study is to develop inorganic scintillators for nuclear medical imaging such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), nuclear and high energy physics experiments, and well logging, etc. For all these applications the scintillator ought to have a fast decay time, good energy resolution, high light yield, excellent proportionality response, a high effective Z number and high density. In addition, its scintillation wavelength spectrum should be well matched with the sensitivity curve of the light sensor. In this study, we will discuss the development and characterization of an elpasolite scintillator that satisfies these characteristics well. We have developed Ce-doped Cs2LiGdBr6 single crystals using by Bridgman method and studied about their scintillation properties as different Ce concentration (10, 15, 20, and 30%). We measured the pulse height and fluorescence decay time spectra of Cs2LiGdBr6:Ce3+ with a bi-alkali photo multiplier tube (PMT) under gamma-ray excitation from 137Cs source. In addition, we measured also the X-ray induced emission spectra by using X-ray generator. Research results showed that the 15% Ce- doped Cs2LiGdBr6 has a fast decay component (t= ~60 ns) and good energy resolution (6.2% at 662 keV) and shows a high scintillation light output (higher than lutetium yttrium orthosilicate). Additionally, the proportional response to this sample was also excellent in the range of 60 keV to 1333 keV gamma energy. The scintillators developed in this study contain lithium and gadolinium which are useful for neutron detection. We report a detail procedure of the crystal growth and scintillation property during this thesis, and consider the prospect for various applications of this scintillator.
Thesis Advisor: Prof. Hongjoo Kim